【摘要】 为了确定荔枝真空冷冻干燥工艺关键技术参数,以成熟的‘乌叶’荔枝为材料,采用电阻法测量荔枝果肉的共晶点和共熔点温度,通过考察冻干品色泽比较不同护色剂的护色效果,以冻干生产能耗、总冻干时间及冻干品外观形态与色泽等指标进行综合评定冻干效果,优选荔枝真空冷冻干燥工艺关键技术参数。结果表明:荔枝真空冷冻干燥物料的共晶点温度、共熔点温度分为-26℃和-17℃,采用"0.6%柠檬酸"单一护色剂或"0.4%柠檬酸+0.2%维生素C"复合护色剂浸泡20min,对荔枝冻干品有良好护色效果。冻干过程起始板温控制在80℃以下,升华阶段物料最高温度设定为55℃,升降温期干燥仓真空值组合选择60~70Pa/60~70Pa,可节省冻干生产能耗、缩短总冻干时间,同时能改善冻干品的外观形态与色泽。更多还原

【Abstract】 In order to confirm the key technology in vacuum freeze-drying of litch,experiments were conducted with litch cultivar‘Wuye’.The eutectic point and the consolute point of litch were determined by electrical resistance method in the vacuum freeze-drying.The different color fixative agents were compared on their color-protecting effects by analysis the color of the freeze-drying products.The key technical parameters of thevacuum freeze-drying of litch were optimized with the freeze-drying effects of the comprehensive indexes being evaluated by energy consumption,freeze-drying time,appearances shape and colors of the products duringthe process of vacuum freeze-drying.The results showed that the eutectic point and the consolute point of lithc’s pulp materials were-26℃and-20.0℃in the vacuum freeze-drying,respectively.In the solution of 0.6%cit?ric acid or 0.4%citric acid+0.2%VC with immersing time for 20 min were gaven the best color-protecting effects.At the condition of first drying temperature under 80℃,material maximum temperature of 50℃duringsublimation stage,and the combination of the vacuum value in drying chamber ranged from 60 Pa to 70 Pa/from 60 Pa to 70 Pa,could save the energy consumption,shorten the freeze-drying time and improved the appearances shape and color of the vacuum freeze-drying products.更多还原